Arrangement for weaken a construction

ABSTRACT

The invention relates to an arrangement F( 1, 1′, 1″ ) for weakening a structure ( 4, 4′,12″ ), comprising at least one element ( 8, 28 ) arranged at the structure ( 4, 4′, 12″ ) to affect its strength, a sensor ( 9 ) arranged to sense impact acting on the structure ( 4, 4′, 12″ ) and a control unit ( 10 ) disposed to, firstly, receive signals from the sensor ( 9 ) and, secondly, emit a control signal when the signal received from the sensor ( 9 ) agrees with a set value. The element ( 8, 28 ) comprises an explosive charge ( 11 ), which is disposed to detonate when said control signal is emitted from the control unit ( 10 ). The explosive charge ( 11 ) is disposed at the element ( 8, 28 ) in such a manner that the element ( 8, 28 ) ewakens the strength of the structure ( 4, 4′, 12″ ) when the explosive charge ( 11 ) detonates.

[0001] The present invention relates to an arrangement for weakening astructure, comprising at least one element, which is arranged at thestructure to affect its strength, a sensor is arranged to sense impactacting on the structure and a control unit is arranged to, firstly,receive signals from the sensor and, secondly, emit a control signalwhen the signal received from the sensor agrees with a set value.

[0002] In a frontal collision between a truck or bus and another truck,for example, the front portion of the cab, together with the instrumentpanel, may be pushed in towards the driver seat due to the enormousforces arising in a collision.

[0003] Trucks typically have a cab arranged on a vehicle frame or achassi. The anchoring of the cab to the vehicle frame is, in certaintruck designs, designed so that the cab will be at least partiallyseparated from the vehicle frame in a head-on collision, so that the cabis pushed backwards. In this way, the cab front portion and theinstrument panel are prevented from being pushed in and injuring thedriver in the cab. Since the cab space will be essentially intact afterthe collision, the cab doors can still be opened, allowing the driver toget out of the cab.

[0004] It is previously known to let the cab separate from the vehicleframe by having one or more beams joining the cab to the vehicle framebe broken off during collision. To achieve this, each beam has afracture indication dimensioned so that the beam is broken off when acertain force is applied to the beam. The beam must, however, also bedimensioned to withstand those stresses acting on the beam during thelife of the truck, e.g. fatigue stresses. It is, however, difficult todimension a beam so that it breaks off when subjected to a certain forcein a collision, at the same time as it withstands fatigue stresses andforces arising during the everyday use of the truck.

[0005] Passenger cars are often designed so that the energy generatedduring collision is absorbed by one or more beams. These beams arecommonly made hollow with a rectangular or square cross section. Duringa collision, the beam is compressed in its axial direction. Such adesign is, however, difficult to apply to trucks.

[0006] Also previously known in trucks are structures comprising beamsheld together by a plurality of screws or rivets. In a collision, thescrews or rivets are broken off by the collision force, and the truckcab is then displaced in the direction of the force. Thus, the truck cabis maintained essentially intact after the collision. It is, however,difficult to dimension the structure so that the screws or rivets arebroken off when subjected to a certain force arising in a collision atthe same time as the structure must be dimensioned so that it can resistfatigue stresses and forces arising during the everyday use of thetruck.

[0007] It is a purpose of the present invention to achieve anarrangement for weakening on a special occasion, a structure made insuch a way that the strength properties of the structure remainunaffected prior to said occasion.

[0008] This is achieved by an arrangement of the type described by wayof introduction where said element comprising an explosive chargedisposed to detonate when said control signal is emitted from thecontrol unit, said explosive charge being arranged at the element insuch a manner that the element weakens the strength of the structurewhen the explosive charge detonates. Such an arrangement means that thestructure does not need to be dimensioned for fracture at a certaincollision force, at the same time as the structure must be strong enoughto withstand the forces arising during everyday use. By virtue of thefact that the element weakens the strength of the structure when anexplosive charge detonates, the structure does not need to bedimensioned for fracture at those forces arising during collision.

[0009] According to one embodiment of the invention the elementcomprises a plurality of fasteners, such as screws, bolts or rivetswhich join a cab to a vehicle frame.

[0010] In a collision, the fasteners are basted off by the explosivecharge. The fasteners can be dimensioned to withstand the forces arisingduring everyday use of the vehicle. Thus, the strength properties of thestructure will be unaffected prior to a collision.

[0011] The invention will be described in more detail below withreference to examples shown in the accompanying drawings, of which

[0012]FIG. 1 shows a first embodiment of an arrangement according to thepresent invention for weakening a truck structure prior to collision,

[0013]FIG. 2 shows the arrangement according to FIG. 1 after the truckhas collided,

[0014]FIG. 3 shows a second embodiment of an arrangement according tothe present invention for weakening a truck structure prior tocollision,

[0015]FIG. 4 shows the arrangement according to FIG. 3 after the truckhas collided,

[0016]FIG. 5 shows how an arrangement according to the present inventioncan be combined with vehicle safety equipment,

[0017]FIG. 6 shows how a beam absorbs energy in a known manner by axialcompression,

[0018]FIG. 7 shows a third embodiment of an arrangement according to thepresent invention for weakening a beam before the beam collides with anobject, and

[0019]FIG. 8 shows the arrangement according to claim 7 after the beamhas collided with the object.

[0020]FIG. 1 shows a first embodiment of an arrangement 1 according tothe present invention. The arrangement 1 comprises at least one element2, which is arranged in a structure 3. According to a first embodiment,the structure 3 is a portion 4 between a vehicle cab 5 and a vehicleframe 6, in a vehicle such as a truck 7. The element 2, which in thisfirst embodiment is a plurality of fasteners 8, such as screws, bolts orrivets, are arranged in a portion 4 to affect its strength. A sensor 9is disposed to sense impact, such as collision impact, against the truck7. A control unit 10 is arranged to firstly receive signals from thesensor 9 and secondly emit a control signal when the signal receivedfrom the sensor 9 agrees with a set value. This set value is programmedinto the control unit 10 and corresponds to an impact occurring in acollision. Preferably, set values corresponding to various collisionsituations and collision directions can be programmed in the controlunit 10.

[0021] Each fastener 8 comprises an explosive charge 11 disposed todetonate when said control signal is emitted from the control unit 10.These explosive charges 11 are so arranged at the fasteners 8 that thefasteners 8 weaken the strength of the structure 3 when the explosivecharges 11 detonate. The explosive substance in the charges 11 can begunpowder, TNT or the like.

[0022]FIG. 1 shows the truck 7 prior to collision. The vehicle cab 5 ismounted on beams 12, which are joined to the vehicle frame 6 via saidportion 4. FIG. 1 shows only one of the beams 12. The fasteners 8 holdthe portion 4 together, so that the beam 12 and thus the cab 5, uponimpact in a collision, are allowed to be displaced relative to thevehicle frame 6 when the explosive charges 11 detonate.

[0023]FIG. 2 shows the truck 7 of FIG. 1 after a collision with anobject 13, which can be another vehicle, a barrier or the like. In acollision, the sensor 9 has detected an impact agreeing with a set valueprogrammed into the control unit 10. The control unit 10 has thenemitted a control signal to the explosive charge 11 of each fastener 8so that all of the fasteners 8 coupled to the control unit 10 have beenbroken off by the detonation of the respective charges 11. The controlsignal is preferably an electrical signal acting on the explosivesubstance of the charge 11 so that it detonates. The portion 4 in theexample shown in FIGS. 1 and 2 consists of two parts 14, 15, which areheld together by three fasteners 8, of which two of the fasteners 8 arecoupled to the control unit 10. The third fastener 8 will be deformed orbroken off by the forces arising during collision and by the cab 5 beingpushed backwards relative to the frame 6. A connecting plate 16 isjoined to the parts 14, 15 of the portion 4, so that the cab 5 aftercollision is prevented from leaving the vehicle frame 6.

[0024] For the purpose of clear illustration, only the front portion ofthe truck 7 is shown in FIGS. 1 and 2. It is thus evident from thefigures how a front wheel 17 is arranged on the frame 6 and how the cab5, with a spring 18 and a damper 19 is suspended on the frame 6. It isalso possible to combine the arrangement 1 according to the presentinvention with vehicle safety equipment, such as one or more collisionairbags 20, as will be explained in more detail below. FIGS. 1 and 2show how the control unit 10 is coupled to an airbag 20 arranged in asteering wheel 21. In order to absorb the energy developed duringcollision, an energy-absorbing element (not shown) can be arrangedbetween the cab 5 and the frame 6. Such an energy-absorbing element can,for example, be a body part connecting a rear section and the cab 5,thereby forming a deformation zone. Such an energy-absorbing element isshown in International Patent Application No. WO-A1-0018633.

[0025]FIGS. 3 and 4 show a second embodiment of an arrangement 1′according to the present invention, which differs from that shown in thefirst embodiment in that the portion 4′, connecting the cab 5 to thevehicle frame 6, is joined with fasteners 8 directly in the beam 12 ofthe cab 5. The fasteners 8 extend horizontally through the portion 4′and the beam 12 of the cab 5. In a collision the fasteners 8 break offin the same manner as was described in connection with the firstembodiment, allowing the portion 4′ to pivot about a joint 22 betweenthe portion 4′ and the beam 12. The cab 5 can thus be displacedrearwardly in this case as well relative to the vehicle frame 6. Thearrangement 1′ according to this second embodiment allows the spacebetween the cab 5 and the frame 6 to be made smaller.

[0026]FIG. 5 illustrates how an arrangement 1, 1′ according to thepresent invention can be combined with security equipment for vehicles.The control unit 10 is coupled by means of electrical cables 23 to theexplosive charges 11 of the fasteners 8. An airbag 20 and a beltpretensioner 24 are also coupled to the control unit 10. The beltpretensioner 24 is intended to tighten a safety belt (not shown) so thatpersons buckled in to the vehicle seats will not be thrown forward in acollision. The control unit 10 can simultaneously send control signalsto the fasteners 8, the airbag 20 and the belt pretensioner 24, so thatthey are all activated simultaneously in a collision. It is alsoconceivable that one or more of these components 8, 20, 24 can beactivated prior to the other components 8, 20, 24 in a collision. Thesensor 9, which senses the impact arising in a collision, is integratedinto the control unit 10 in the embodiment shown in FIG. 5.

[0027] Additional embodiments of the invention will be described below.FIG. 6 shows how a beam 12″ absorbs energy in a known manner by beingcompressed axially in a collision. Such beams 12″ are often present inpassenger cars and are usually made hollow with a rectangular or squarecross section. A body 25 having a certain mass is arranged at one end 26of the beam 12″. At the moment of collision, the beam 12″ and the body25 are moving a velocity v1. As was mentioned in the introduction to thedescription, such known beams 12″ are, however, difficult to use intrucks 7. Certain types of trucks 7 are not provided with a deformationzone in front of the cab 5, and therefore there is no space to place oneor more elongated beams 12″ in front of the cab 5.

[0028]FIG. 7 shows a third embodiment of a device 1″ according to thepresent invention for weakening a structure in the form of a beam 12″,before the beam 12″ collides with an object 13. The beam 12″ can have asquare, rectangular or circular cross-section. The cross section canalso have an arbitrary shape.

[0029] An element is arranged on the beam 12″ to affect the strength ofthe beam 12″. The element in this case is a piston 28 displaceable in acylinder 27. An explosive charge 11 disposed next to the cylinder 27displaces the piston 28 in the cylinder 27 when it detonates, causing apiston rod 29 joined to the piston 28 to deform the beam 12″, therebyweakening it.

[0030]FIG. 8 shows how the beam 12″ according to FIG. 7 has collidedwith the object 13. At the moment of collision, the beam 12″ and a body25 connected to the beam 12″ move at a velocity v2. A sensor 9 isdisposed on the beam 12″ to sense impact against the beam 12″, and acontrol unit 10 is arranged to, firstly, receive signals from the sensor9, and, secondly, to emit a control signal when the signal received fromthe sensor 9 agrees with a set value. The explosive charge 11 isdisposed to detonate when said control signal is emitted from thecontrol unit 10. Detonation causes gases to be pressed into the cylinder27, moving the piston 28 towards a first end 30 of the cylinder 27. Oneend 32 of the piston rod 29 is joined to an anchor 33 abutting orconnected to one side of the beam 12″. The other end 34 of the cylinder27 abuts against the opposite side of the beam 12″. By making anchor 33with a smaller abutment surface against the beam 12″ than the second end34 of the cylinder 27, the beam 12″ will be deformed in a controlledmanner. When the arrangement 1″ according to the invention weakens thestrength of the beam 12″, the mass of the body 25 and the velocity v2will affect a section 31 of the beam 12″, bending this section 31 with avelocity v3 in a direction essentially perpendicular to the axialdirection of the beam 12″. Thus, a portion of the energy and forcegenerated during collision will be diverted in another direction thanthe direction of travel of the beam 12″ and the body 25 prior tocollision. Preferably, the deformation of the beam 12″ is controlledwith the aid of the piston rod 29″ and the cylinder 27 to obtain acontrolled absorption of the energy generated during collision. This canbe achieved by adjusting the deformation of the beam 12″ by the pistonrod 29″ and the cylinder 27 proportionally to the magnitude of the pulsegenerated during collision. The magnitude of this pulse is detected bythe sensor 9, which sends signals to the control unit 10 to displace thepiston 28 a certain distance in the cylinder 27. According to this lastmentioned embodiment, a structure 3, such as a beam 12″ or anothermechanical element can be weakened in a passenger car, a truck, or othervehicle in order to reduce the negative consequences of a collision.

1. Arrangement for weakening a portion (4, 4′) of a vehicle (7),comprising at least one element (8), which is arranged at the portion(4, 4′) to affect its strength, said portion (4, 4′) being disposedbetween a beam (12) of a vehicle cab (5) and a vehicle frame (6), saidportion being joined to the element (8), so that the beam (12), and withit the vehicle cab (5), upon impact in a collision, can be displacedrelative to the vehicle frame (6), characterized in that a sensor (9) isarranged to sense impact acting on the portion (4, 4′), and a controlunit (10) is arranged to, firstly, receive signals from the sensor (9)and, secondly, emit a control signal when the signal received from thesensor (9) agrees with a set value, said element (8) comprising anexplosive charge (11) disposed to detonate when said control signal isemitted from the control unit (10), said explosive charge (11) beingarranged at the element (8) in such a manner that the element (8)weakens the strength of the portion (4, 4′) when the explosive charge(11) detonates, thereby allowing the cab (5) to be displaced, by theimpact generated in the collision, relative to the vehicle frame (6)when the explosive charge (11) detonates.
 2. Arrangement according toclaim 1, characterized in that the element consists of at least onefastener (8) joined to the structure, said fastener being disposed to bebroken off when the explosive charge (11) detonates.
 3. Arrangementaccording to claim 2, characterized in that the fastener (8) is a screw,bolt or rivet.
 4. Arrangement according to one of the preceding claims,characterized in that the sensor (9) is disposed to emit signals to atleast an airbag (20) arranged in a vehicle cab (5) and/or a beltpretensioner (24).
 5. Arrangement according to one of the precedingclaims, characterized in that a piston (28) displaceable in a cylinderis disposed to deform, with a piston rod (29) joined to the piston (28),a structure (12″), which is thereby weakened, by virtue of the fact thatthe detonation of the explosive charge (11) displaces the piston (28) inthe cylinder (27).
 6. Arrangement according to one of the precedingclaims, characterized in that a plurality of set values, correspondingto various collision sequences, are programmed into the control unit(10).